[Wireless Communication Network Between Terminals]
It is useful to autonomously construct and operate wireless communication between terminals in a limited geographic area. For example, in a disaster site or the like, autonomous wireless communication constructed between terminals is useful because of reasons such as a wireless communication service provided by a network provider cannot be used due to a failure, speedy and secure communication cannot be realized when the wireless communication service is shared by an unspecified large number of subscribers, and so on.
Such a wireless communication network between terminals is used by, for example, a local government, a police station, a fire department, the self-defense force, and the like. Such a wireless communication network between terminals is also useful for various terminals located in a limited geographic area for various academic, recreational, and commercial activities held indoors and outdoors.
In a wireless communication network in which a terminal moves, a handover technique is required so as to secure communication between terminals.
[Handover Between Base Stations]
In the field of wireless communication networks, a handover technique in which a base station to which a terminal is coupled is switched is known.
In Wireless Local Loop (WLL) using a Fixed Subscriber Unit (FSU), a method for continuously capturing an optimal wireless base station is known. In this method, the FSU periodically measures a reception level of a base station around the FSU, and transmits a message indicating the reception level to the base station. The base station transmits an updated list of base stations that can be assigned to the FSU on the basis of the message. The FSU realizes an assignment by using base stations listed on the updated list.
A method for reducing the time of handover that switches a base station with which a terminal communicates while the terminal is moving is known. In this method, in time-division multiplexing wireless communication, a predetermined number of slots in one frame are allocated to preliminary communication for handover.
In a system based on WiMAX (Worldwide Interoperability for Microwave Access), FBSS (Fast-BS-Switch) is known as a technique in which a terminal synchronizes with a plurality of base stations and fast handover is realized among the base stations.
Japanese Unexamined Patent Application Publication No. 2001-160989 and Japanese Unexamined Patent Application Publication No. 2001-28775 are examples of related art.